Refrigerator

ABSTRACT

A refrigerator includes a Stirling refrigerating machine having a high-temperature heat radiation portion and a low-temperature heat absorption portion and for cooling a freezing compartment, and a compressor for circulating a first refrigerant through a first circulation circuit having a cooling compartment evaporator. The high-temperature heat radiation portion is in contact with a first circulation spiral portion formed in the first circulation circuit.

TECHNICAL FIELD

The present invention relates to a refrigerator incorporating a Stirlingrefrigerating machine and a compressor.

BACKGROUND ART

A conventional refrigerator employs a refrigeration cycle using acompressor. The compressor is used for condensing a working refrigerantin the refrigeration cycle. The condensed working refrigerant is reducedin pressure and expanded in an expansion portion, and is delivered to anevaporator. The evaporator attains a low temperature as the workingrefrigerant evaporates therein. The evaporator is arranged inside therefrigerator, and the interior of the refrigerator is maintained at alow temperature by the evaporator. For the working refrigerant, analternative refrigerant (HFC refrigerant) or hydrocarbon (HCrefrigerant) is used.

A refrigerator provided with a Stirling refrigerating machine using areversed Stirling cycle instead of the refrigeration cycle using thecompressor has been proposed (e.g., Japanese Patent Laying-Open No.2000-18748). A refrigerator incorporating both the Stirlingrefrigerating machine and the compressor has been proposed as well.

FIG. 4 is a schematic cross sectional view of a refrigeratorincorporating a Stirling refrigerating machine and a compressor that isdisclosed in Japanese Patent Laying-Open No. 2000-337747. Therefrigerator is partitioned into a cooling compartment 21 and a freezingcompartment 22, with freezing compartment 22 being arranged on the upperside and cooling compartment 21 being arranged on the lower side. Acompressor 11 is arranged in the back at the bottom of coolingcompartment 21. The refrigerant compressed by compressor 11 is deliveredvia a first circulation circuit 5 to a heat exchanger 29. Cooling andexpansion of the refrigerant take place (not shown) between compressor11 and heat exchanger 29. The refrigerant having reached heat exchanger29 is evaporated within heat exchanger 29, which cools heat exchanger 29by latent heat. The refrigerant having been evaporated in the coolingcompartment evaporator is returned via first circulation circuit 5 tocompressor 11, where it is compressed again.

At the back of cooling compartment 21, a cooling compartment circulationpath 8 is formed for circulation of the air in cooling compartment 21.Heat exchanger 29 is arranged inside cooling compartment circulationpath 8. Also arranged in cooling compartment circulation path 8 is acooling compartment cooling fan 23. As cooling compartment cooling fan23 is driven, the air flow occurs inside cooling compartment circulationpath 8. In FIG. 4, the air in cooling compartment 21 enters coolingcompartment circulation path 8 from the lower side and is released intocooling compartment 21 from an outlet formed in cooling compartmentcirculation path 8. The air within cooling compartment 21 is cooled asit comes into contact with heat exchanger 29 when passing throughcooling compartment circulation path 8. The air coming out of coolingcompartment circulation path 8 has been cooled and is of a lowtemperature. This air flow cools the items stored in cooling compartment21.

Stirling refrigerating machine 1 is arranged in the back at the top ofthe refrigerator. Stirling refrigerating machine 1 is a device in whicha piston performs a reciprocating motion inside the cylinder, whichcauses the working refrigerant to move between a compression space andan expansion space to thereby repeat compression and expansion. As theworking refrigerant, helium gas, hydrogen gas, nitrogen gas or the likeis filled therein. The working refrigerant compressed in the compressionspace is at a high temperature, which is cooled by the outside air at ahigh-temperature heat radiation portion 2. The cooled workingrefrigerant is expanded as it is transferred to the expansion space. Theworking refrigerant attains a low temperature as it is expanded in theexpansion space. The working refrigerant of a low temperature cools alow-temperature heat absorption portion 3. Low-temperature heatabsorption portion 3 is formed such that a part thereof is exposed tofreezing compartment 22. Freezing compartment 22 is cooled bylow-temperature heat absorption portion 3.

In the refrigerator shown in FIG. 4, cooling compartment circulationpath 8 extends to the top portion of the refrigerator where Stirlingrefrigerating machine 1 is arranged. Further, a blower fan 25 isarranged to deliver the cool air toward the top portion of therefrigerator. This refrigerator is configured such that driving of bowerfan 25 can deliver a part of the air cooled by heat exchanger 29 to thehigh-temperature heat radiation portion of the Stirling refrigeratingmachine. High-temperature heat radiation portion 2 is cooled by this airof a low temperature. The air having cooled high-temperature heatradiation portion 2 is externally discharged via an exhaust vent 26formed on the backside of the refrigerator.

Since this refrigerator has freezing compartment 22 cooled by Stirlingrefrigerating machine 1 and cooling compartment 22 cooled by heatexchanger 29, the respective compartments can be used in accordance withthe intended use, so that a refrigerator of high usability is obtained.Further, the air in cooling compartment circulation path 8 having beencooled by heat exchanger 29 can cool high-temperature heat radiationportion 2 of Stirling refrigerating machine 1, and as a result, coolingefficiency of Stirling refrigerating machine 1 is improved.

Patent Document 1: Japanese Patent Laying-Open No. 2000-18748 (pages4-5, and FIGS. 1-6)

Patent Document 2: Japanese Patent Laying-Open No. 2000-337747 (pages3-4, and FIGS. 1-2)

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

In a refrigerator using only the refrigeration cycle by the compressor,when the refrigeration cycle attains a temperature in the cryogenictemperature range of −30° C. or lower, cooling capacity is considerablydecreased as the specific volume and the compression ratio of therefrigerant vapor increase. As such, it is difficult to employ it as arefrigerator performing cryogenic refrigeration.

Although a refrigerator incorporating only the Stirling refrigeratingmachine can handle the refrigeration in the cryogenic temperature range,using the cold air of −30° C. or lower for cooling the coolingcompartment of 0° C. to 5° C. would increase power consumption of therefrigerator as a whole. Further, unlike the case of the refrigeratorusing the refrigeration cycle by the compressor, it would be difficultto utilize the heat of the high-temperature heat radiation portion ofthe Stirling refrigerating machine directly for preventing formation ofdew condensation at the door gasket of the refrigerator or for treatmentof the drain water. Although the heat of the high-temperature heatradiation portion of the Stirling refrigerating machine may be utilizedfor heating the door gasket or the drain pan using a heat pipe or asecondary refrigerant circulation pump, system COP (energy consumptionefficiency: Coefficient of Performance) will be degraded due to poorheat exchange efficiency.

Meanwhile, in the refrigerator disclosed in Japanese Patent Laying-OpenNo. 2000-337747, the air of a low temperature-having been generated inthe refrigeration cycle by the compressor is utilized directly forcooling the high-temperature heat radiation portion of the Stirlingrefrigerating machine, to thereby improve cooling efficiency of thehigh-temperature heat radiation portion of the Stirling refrigeratingmachine. This refrigerator however is poor in efficiency of heatexchange since the heat-transfer coefficient of the air is low. The coldair would be released to the environment in a large amount, leading todegradation of the system COP. Further, since the air is cooled at theheat exchanger in the refrigeration cycle using the compressor and thecooled air is then used to cool the high-temperature heat radiationportion of the Stirling refrigerating machine, it takes time until thetemperature of the high-temperature heat radiation portion of theStirling refrigerating machine is lowered, which is unsuitable for quickcooling of the freezing compartment.

The present invention has been made to solve the above-describedproblems, and an object of the present invention is to provide arefrigerator capable of cryogenic refrigeration with low powerconsumption.

Means for Solving the Problems

A refrigerator according to the present invention includes a Stirlingrefrigerating machine having a high-temperature heat radiation portionand a low-temperature heat absorption portion and cooling a freezingcompartment, and a compressor for circulating a first refrigerantthrough a first circulation circuit including a cooling compartmentevaporator. The high-temperature heat radiation portion is in contactwith the first circulation circuit. With this configuration, it ispossible to efficiently cool the high-temperature heat radiation portionof the Stirling refrigerating machine, and thus to provide arefrigerator capable of cryogenic refrigeration with low powerconsumption.

In the above invention, preferably, the high-temperature heat radiationportion is in contact with piping of the first circulation circuit onits way from the cooling compartment evaporator back to the compressor.With this configuration, it is possible to cause the high-temperatureheat radiation portion to come into contact with the first circulationcircuit with a simple configuration.

In the above invention, preferably, the high-temperature heat radiationportion is in contact with a heat radiation portion cooling evaporatorthat is formed in the first circulation circuit on its way from thecooling compartment evaporator back to the compressor. With thisconfiguration, it is possible to enlarge the contact area between thehigh-temperature heat radiation portion and the first circulationcircuit, and thus to cool the high-temperature heat radiation portionmore efficiently.

In the above invention, preferably, a cooling compartment cooling fan isprovided for transferring cold heat of the cooling compartmentevaporator to a cooling compartment, and control means is also providedfor stopping the cooling compartment cooling fan when detecting that atemperature of the freezing compartment has become a set value orhigher. With this configuration, it is possible to quickly cool thefreezing compartment even if the temperature of the freezing compartmentbecomes high.

In the above invention, preferably, the first circulation circuitincludes a main circuit and an auxiliary circuit. The auxiliary circuithas an auxiliary refrigerant expansion portion and a heat radiationportion cooling evaporator that is formed downstream of the auxiliaryrefrigerant expansion portion, and has its inlet connected to branchmeans that is formed in piping of the main circuit on its way from thecompressor to the cooling compartment evaporator. The high-temperatureheat radiation portion is in contact with the heat radiation portioncooling evaporator. With this configuration, it is possible to use apart of the first refrigerant for cooling the high-temperature heatradiation portion, and thus to cool the high-temperature heat radiationportion more efficiently.

In the above invention, preferably, a three-way valve capable ofopening/closing its side directed to the cooling compartment evaporatorand its side directed to the heat radiation portion cooling evaporatoris arranged as the branch means. With this configuration, the branchmeans can readily be formed. Further, it is possible to block the firstrefrigerant going toward the cooling compartment evaporator or the firstrefrigerant going toward the heat radiation portion cooling evaporatoras required, which leads to saving of power consumption.

In the above invention, preferably, control means is provided forclosing the side of the three-way valve directed to the coolingcompartment evaporator when detecting that a temperature of the coolingcompartment has become a set value or lower. With this configuration,when it is unnecessary to cool the cooling compartment, the flow of thefirst refrigerant toward a cooling compartment evaporator can be blockedto save power consumption.

In the above invention, preferably, control means is provided forclosing the side of the three-way valve directed to the heat radiationportion cooling evaporator when detecting that a temperature of thefreezing compartment has become a set value or lower. With thisconfiguration, when it is unnecessary to cool the freezing compartment,the flow of the first refrigerant toward the heat radiation portioncooling evaporator can be blocked to save power consumption.

In the above invention, preferably, control means is provided forclosing the side of the three-way valve directed to the coolingcompartment evaporator and opening the side of the three-way valvedirected to the heat radiation portion cooling evaporator when detectingthat a temperature of the freezing compartment has become a set value orhigher. With this configuration, it is possible to increase the coolingcapacity of the heat radiation portion cooling evaporator, to therebyquickly cool the freezing compartment.

In the above invention, preferably, a cooling compartment cooling fan isprovided for transferring cold heat of the cooling compartmentevaporator to a cooling compartment, and control means is provided forcausing the cooling compartment cooling fan to rotate by detectinghumidity of the cooling compartment in the state where the side of thethree-way valve directed to the cooling compartment evaporator isclosed. With this configuration, it is possible to evaporate the frostsettled around the cooling compartment evaporator, to thereby maintainsufficiently high humidity in the cooling compartment.

In the above invention, preferably, control means is provided fordecreasing the number of revolutions of the compressor and increasingoutput of the Stirling refrigerating machine when detecting that atemperature of the cooling compartment evaporator has become a set valueor lower. With this configuration, it is possible to remove the frostformed around the cooling compartment evaporator, which eliminates theneed of a defrosting heater otherwise provided around the coolingcompartment evaporator. This simplifies the device configuration, andcan save power consumption as well.

In the above invention, preferably, control means is provided forcontrolling the number of revolutions of the compressor in response toan outside air temperature and a temperature of a cooling compartment.With this configuration, it is possible to suppress an operation of thecompressor in the state where excessive load is involved, whichcontributes to saving of power consumption.

Effects of the Invention

According to the present invention, it is possible to provide arefrigerator consuming low power and capable of cryogenic refrigeration,which can efficiently cool a high-temperature heat radiation portion ofa Stirling refrigerating machine.

Further, it is possible to provide a refrigerator ensuring high poweroutput even when a low-temperature heat absorption portion of theStirling refrigerating machine is in a cryogenic state, and enablinglong-lasting cryogenic cooling of the freezing compartment as well asquick refrigeration of the freezing compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cooling circuit of a refrigerator according to afirst embodiment of the present invention.

FIG. 2 is a schematic cross sectional view of the refrigerator accordingto the first embodiment of the present invention.

FIG. 3 illustrates a cooling circuit of a refrigerator according to asecond embodiment of the present invention.

FIG. 4 is a schematic cross sectional view of a refrigerator accordingto a conventional art.

DESCRIPTION OF THE REFERENCE SIGNS

1: Stirling refrigerating machine; 2: high-temperature heat radiationportion; 3: low-temperature heat absorption portion; 4: freezingcompartment evaporator; 5: first circulation circuit; 6: secondcirculation circuit; 7 a: main circuit; 7 b : auxiliary circuit; 8:cooling compartment circulation path; 9: freezing compartmentcirculation path; 11: compressor; 12: cooling compartment evaporator; 13a: refrigerant expansion portion; 13 b: auxiliary refrigerant expansionportion; 14: drain treatment refrigerant pipe; 15: dew condensationpreventing refrigerant pipe; 16: refrigerant condensation pipe; 17:first circulation spiral portion; 18: second circulation spiral portion;19: heat radiation portion cooling evaporator; 20: three-way valve; 21:cooling compartment; 22: freezing compartment; 23: cooling compartmentcooling fan; 24: freezing compartment cooling fan; 25: blower fan; 26:exhaust vent; 27, 28: partition; and 29: heat exchanger.

BEST MODES FOR CARRYING OUT THE INVENTION

A refrigerator according to a first embodiment of the present inventionwill now be described with reference to FIGS. 1 and 2.

FIG. 1 illustrates a cooling circuit of the refrigerator of the presentembodiment. The refrigerator is provided with a refrigeration cycleincluding a compressor 11, and a Stirling refrigerating machine 1. Thecooling circuit includes a first circulation circuit 5 and a secondcirculation circuit 6. HC refrigerant as the first refrigerant is filledin first circulation circuit 5, while carbon dioxide as the secondrefrigerant is filled in second circulation circuit 6.

First circulation circuit 5 is configured such that the firstrefrigerant is compressed by compressor 11, delivered to a coolingcompartment evaporator 12 as shown by an arrow 31, and returned tocompressor 11 via a first circulation spiral portion 17 as shown by anarrow 32. Stirling refrigerating machine 1 includes a high-temperatureheat radiation portion 2 and a low-temperature heat absorption portion3, and helium, nitrogen or hydrogen gas is sealed therein. Secondcirculation circuit 6 is formed to come into contact withlow-temperature heat absorption portion 3 at a second circulation spiralportion 18, and is configured such that the second refrigerant is sentto a freezing compartment evaporator 4 as shown by an arrow 33, and thenreturned to second circulation spiral portion 18 as shown by an arrow34.

In first circulation circuit 5, a drain treatment refrigerant pipe 14, adew condensation preventing refrigerant pipe 15, a refrigerantcondensation pipe 16, and a refrigerant expansion portion 13 a areconnected in series between the outlet of compressor 11 and the inlet ofcooling compartment evaporator 12. For refrigerant expansion portion 13a, a capillary tube (tubule), an expansion valve or the like may beemployed. A first circulation spiral portion 17 is formed between theoutlet of cooling compartment evaporator 12 and the inlet of compressor11, which is made of the piping of first circulation circuit 5 wound ina spiral manner. First circulation spiral portion 17 is formed tosurround high-temperature heat radiation portion 2 of Stirlingrefrigerating machine 1 to come into contact therewith. Secondcirculation spiral portion 18 of second circulation circuit 6 is formedaround low-temperature heat absorption portion 3 of Stirlingrefrigerating machine 1 to come into contact with low-pressure heatabsorption portion 3.

FIG. 2 is a schematic cross sectional view of the refrigerator of thepresent embodiment. The refrigerator of the present embodiment has acooling compartment 21 and a freezing compartment 22, with coolingcompartment 21 on the upper side and freezing compartment 22 on thelower side. Compressor 11 is arranged at the lower part in the back ofthe refrigerator. Stirling refrigerating machine 1 is arranged at theupper part in the back of the refrigerator. Stirling refrigeratingmachine 1 is arranged isolated from cooling compartment 21. A partition28 is arranged at the back of freezing compartment 22 to form a freezingcompartment circulation path 9. A freezing compartment evaporator 4 anda freezing compartment cooling fan 24 are arranged inside freezingcompartment circulation path 9. A partition 27 is arranged at the backof cooling compartment 21 to form a cooling compartment circulation path8. Partition 27 also divides cooling compartment 21 into an upper partand a lower part. A cooling compartment evaporator 12 and a coolingcompartment cooling fan 23 are arranged inside cooling compartmentcirculation path 8.

First circulation circuit 5 connected to compressor 11 is passed throughthe bottom part of the refrigerator and is guided frontward of therefrigerator. First circulation circuit 5 guided frontward is thenpassed through the inside of a side panel formed on the side face of therefrigerator, and is guided again to the back part, where it isconnected to the inlet of cooling compartment evaporator 12. The draintreatment refrigerant pipe (not shown) is placed at the bottom part ofthe refrigerator. The condensation preventing refrigerant pipe (notshown) is placed around the opening of the refrigerator. The refrigerantcondensation pipe (not shown) is placed inside the side panel, attachedthereto in a meandering pattern. The refrigerant expansion portion (notshown) is formed of a capillary tube, which is placed between therefrigerant condensation pipe and cooling compartment evaporator 12.First circulation circuit 5 connected to the outlet of coolingcompartment evaporator 12 is configured such that it returns tocompressor 11 via first circulation spiral portion 17 (see FIG. 1) incontact with high-temperature heat radiation portion 2 of Stirlingrefrigerating machine 1 that is arranged at the upper part.

Second circulation circuit 6 is formed at the back part of therefrigerator. Second circulation circuit 6 having come out of secondcirculation spiral portion 18 (see FIG. 1) in contact withlow-temperature heat absorption portion 3 of Stirling refrigeratingmachine 1 is connected to the inlet of freezing compartment evaporator 4that is arranged in freezing compartment circulation path 9. Secondcirculation circuit 6 connected to the outlet of freezing compartmentevaporator 4 is connected to the inlet of second circulation spiralportion 18 (see FIG. 1).

The first refrigerant coming out of compressor 11 is passed throughdrain treatment refrigerant pipe 14, dew condensation preventingrefrigerant pipe 15 and refrigerant condensation pipe 16, and deliveredto refrigerant expansion portion 13 a. The first refrigerant condensedin compressor 11 has its temperature increased, which is cooled as it ispassed through drain treatment refrigerant pipe 14, dew condensationpreventing refrigerant pipe 15 and refrigerant condensation pipe 16.Drain treatment refrigerant pipe 14 serves to evaporate the drain waterof the refrigerator, while dew condensation preventing refrigerant pipe15 prevents formation of dew condensation at the door gasket and theperipheral portion of the refrigerator. Refrigerant condensation pipe 16releases the heat of the first refrigerant to the outside of therefrigerator via the side panel of the refrigerator. With such heatexchange, the first refrigerant is cooled and condensed before itreaches refrigerant expansion portion 13 a. In the present embodiment,the heat radiation pipes are formed in straight lines connected inseries, for simplification of explanation. Not limited thereto, they mayeach include a parallel circuit having curved portions, or more than onepipe or parallel circuit may be formed.

The first refrigerant cooled while flowing through first circulationcircuit 5 is reduced in pressure and expanded in refrigerant expansionportion 13 a, and is delivered to cooling compartment evaporator 12 inthe two-phase state. Cooling compartment evaporator 12 attains a lowtemperature by latent heat as the first refrigerant evaporates. Thefirst refrigerant coming out of cooling compartment evaporator 12 isdelivered to first circulation spiral portion 17 as shown by an arrow 32in FIG. 1. High-temperature heat radiation portion 2 of Stirlingrefrigerating machine 1 is cooled as first circulation spiral portion 17is in contact with high-temperature heat radiation portion 2.Thereafter, the first refrigerant is returned to compressor 11, where itis compressed again.

When compressor 11 starts operation, the first refrigerant inside firstcirculation circuit 5 begins to circulate, and cooling compartmentevaporator 12 attains a low temperature. The air flow shown by arrows41, 42 and 43 is generated as cooling compartment cooling fan 23 isdriven. The air in cooling compartment 21 flows into cooling compartmentcirculation path 8, where it is cooled by cooling compartment evaporator12 and then returned to cooling compartment 21. In the presentembodiment, cooling compartment 21 is separated into the upper part andthe lower part by partition 27. Thus, in cooling compartment 21, the airflow occurs from the upper rack to the lower rack of cooling compartment21 as shown by arrow 43. As such, the air cooled by cooling compartmentevaporator 12 is circulated inside cooling compartment 21 to therebycool the whole area inside cooling compartment 21.

Meanwhile, Stirling refrigerating machine 1 is activated to coolfreezing compartment 22. When Stirling refrigerating machine 1 isactivated, the temperature of high-temperature heat radiation portion 2increases, while the temperature of low-temperature heat absorptionportion 3 decreases. Second circulation spiral portion 18 (see FIG. 1)formed around low-temperature heat absorption portion 3 is cooled, andthe second refrigerant therein is condensed. The second refrigerantflows downward to freezing compartment evaporator 4 arranged at thelower part. The second refrigerant having flown into freezingcompartment evaporator 4 is evaporated therein, which causes freezingcompartment evaporator 4 to reach a low temperature. The secondrefrigerant coming out of freezing compartment evaporator 4 moves towardsecond circulation spiral portion 18 formed on the upper side in thevertical direction by the process of natural circulation, where it isagain cooled and condensed. As such, the second refrigerant circulatesinside second circulation circuit 6 to lower the temperature of freezingcompartment evaporator 4.

As freezing compartment cooling fan 24 is driven, the air in thefreezing compartment flows into freezing compartment circulation path 9as shown by an arrow 44. The air flowing in performs heat exchange withfreezing compartment evaporator 4, so that it becomes the air of a lowtemperature. Thereafter, it is released to the inside of freezingcompartment 22 as shown by an arrow 45. This cools the inside offreezing compartment 22 to allow it to maintain the cryogenic state.

As Stirling refrigerating machine 1 is driven, the temperature ofhigh-temperature heat radiation portion 2 increases. In the refrigeratorof the present embodiment, high-temperature heat radiation portion 2 isin contact with the piping of first circulation circuit 5 on its wayfrom cooling compartment evaporator 12 back to compressor 11. With thisconfiguration, it is possible to forcibly cool high-temperature heatradiation portion 2 with the cold heat of first circulation circuit 5,and thus, heat exchange can be performed quickly and efficiently. As aresult, power consumption of Stirling refrigerating machine 1 can belowered, and the system COP can be improved. Further, high power outputcan be obtained even if the low-temperature heat absorption portion ofthe Stirling refrigerating machine is in the cryogenic state, and thecryogenic cooling of the freezing compartment can be maintained for along period of time.

In the present embodiment, first circulation spiral portion 17 (seeFIG. 1) is formed at the contact portion between high-temperature heatradiation portion 2 and first circulation circuit 5. The configurationhowever is not specifically limited thereto. All that is needed is thatfirst circulation circuit 5 and high-temperature heat radiation portion2 are in contact with each other over a large area. Alternatively, firstcirculation spiral portion 17 may be replaced with an evaporator, wherethe first refrigerant may be evaporated again to cool high-temperatureheat radiation portion 2 by latent heat thereof That is, a heatradiation portion cooling evaporator may be formed aroundhigh-temperature heat radiation portion 2 to come into contacttherewith. By forming the evaporator, heat exchange withhigh-temperature heat radiation portion 2 can be performed efficiently.Further, the contact area with high-temperature heat radiation portion 2can be made large, which improves efficiency of heat exchange.

In the present embodiment, second circulation spiral portion 18 (seeFIG. 1) is formed at the contact portion between low-temperature heatabsorption portion 3 and second circulation circuit 6. The configurationhowever is not specifically limited thereto. All that is needed is thatheat exchange is enabled between low-temperature heat absorption portion3 and second circulation circuit 6. For example, in place of secondcirculation spiral portion 18, a condenser may be provided in closecontact with low-temperature heat absorption portion 3. By forming thecondenser, heat exchange with low-temperature heat absorption portion 3can be performed efficiently. Alternatively, in the second circulationcircuit, the piping or the freezing compartment evaporator may bereplaced with heat transfer means such as a heat pipe or a heat sink.

The refrigerator of the present embodiment is provided with controlmeans for stopping cooling compartment cooling fan 23 when detectingthat the temperature of freezing compartment 22 has become a presetvalue or greater. For example, assume that there is a necessity torapidly cool freezing compartment 22 since the temperature of freezingcompartment 22 has increased because of the door of freezing compartment22 left open for a long period of time. In such a case, the temperatureof freezing compartment 22 is detected and cooling compartment coolingfan 23 is stopped. Heat exchange around cooling compartment evaporator12 becomes dependent on natural convection, which means less frequentheat exchange. As a result, the temperature of first circulation circuit5 as a whole decreases, and high-temperature heat radiation portion 2 ofStirling refrigerating machine 1 can be cooled more powerfully in firstcirculation spiral portion 17. Accordingly, it is possible to increasecooling capacity of low-temperature heat absorption portion 3, to enablerapid cooling of the inside of freezing compartment 22.

Further, the refrigerator of the present embodiment is provided withcontrol means for lowering the number of revolutions of compressor 11and for increasing the output of Stirling refrigerating machine 1 whendetecting that the temperature of cooling compartment evaporator 12 hasbecome a preset value or lower. When the temperature of coolingcompartment evaporator 12 becomes too low, there occurs frost aroundcooling compartment evaporator 12. In such a case, the temperature ofthe first refrigerant in first circulation circuit 5 increases when thenumber of revolutions of compressor 11 is lowered. As such, thetemperature of cooling compartment evaporator 12 increases as well. Inaddition, when the output of Stirling refrigerating machine 1 increases,the temperature of high-temperature heat radiation portion 2, as well asthe temperature of first circulation spiral portion 17 increases. Thatis, increasing the output of the Stirling refrigerating machine canaccelerate the increase in temperature of the first refrigerant. Byproviding such control means, the frost formed around coolingcompartment evaporator 12 can be removed. As a result, a defrostingheater having conventionally been attached to cooling compartmentevaporator 12 becomes unnecessary. This can simplify the deviceconfiguration and also save power consumption.

Further, the refrigerator of the present embodiment includes means fordetecting the outside air temperature (the ambient temperature aroundthe refrigerator) and the temperature of the cooling compartment, andfor controlling the number of revolutions of the compressor inaccordance with the outside air temperature and the temperature of thecooling compartment. With this configuration, cooling can be carried outefficiently, which contributes to saving of power consumption.

In the present embodiment, the HC refrigerant is used for the firstrefrigerant, and carbon dioxide is used for the second refrigerant.Using these refrigerants, the refrigerator according to the presentinvention can be provided without using chlorofluorocarbon that maydestroy the global environment.

A refrigerator according to a second embodiment of the present inventionwill now be described with reference to FIG. 3. FIG. 3 illustrates acooling circuit of the refrigerator of the present embodiment.

The refrigerator of the present embodiment is similar to therefrigerator of the first embodiment in that it includes coolingcompartment evaporator 12 connected to compressor 11 and freezingcompartment evaporator 4 connected to Stirling refrigerating machine 1.Positioning of compressor 11, Stirling refrigerating machine 1, coolingcompartment evaporator 12 and freezing compartment evaporator 4 withinthe refrigerator is also similar to that of the first embodiment.

First circulation circuit 5 of the present embodiment includes a maincircuit 7 a and an auxiliary circuit 7 b. Main circuit 7 a is a circuitwhere the refrigerant circulates through compressor 11, heat radiatorssuch as drain treatment refrigerant pipe 14, refrigerant expansionportion 13 a, and cooling compartment evaporator 12. The firstrefrigerant coming out of cooling compartment evaporator 12 is returneddirectly to compressor 11. The inlet of auxiliary circuit 7 b isconnected to a three-way valve 20 serving as branch means that is formedin the piping of main circuit 7 a on its way from compressor 11 tocooling compartment evaporator 12. The outlet of auxiliary circuit 7 bis connected to main circuit 7 a on its way from cooling compartmentevaporator 12 back to compressor 11. Auxiliary circuit 7 b includes anauxiliary refrigerant expansion portion 13 b for expanding the firstrefrigerant in main circuit 7 a while reducing its pressure, and a heatradiation portion cooling evaporator 19 that is in contact withhigh-temperature heat radiation portion 2 of Stirling refrigeratingmachine 1. Heat radiation portion cooling evaporator 19 is formeddownstream of auxiliary refrigerant expansion portion 13 b. Auxiliarycircuit 7 b is arranged on the backside of the refrigerator.

Three-way valve 20 serving as the branch means is formed betweenrefrigerant condensation pipe 16 and refrigerant expansion portion 13 a.Three-way valve 20 used herein is one having four modes allowingopening/closing of the side directed to cooling compartment evaporator12 and the side directed to heat radiation portion cooling evaporator19. Although three-way valve 20 used in the present embodiment enablesonly full opening and full closing in the respective directions, onecapable of adjusting the degree of opening in each direction may also beemployed.

Heat radiation portion cooling evaporator 19 is formed in contact withhigh-temperature heat radiation portion 2 to surround the same. A secondcirculation spiral portion 18 is formed around low-temperature heatabsorption portion 3 of Stirling refrigerating machine 1, which is in aspiral shape in contact with low-temperature heat absorption portion 3surrounding the same. Second circulation circuit 6, as in the case ofthe first embodiment, is formed such that the second refrigerant cancirculate between second circulation spiral portion 18 and freezingcompartment evaporator 4. In the present embodiment, HC refrigerant isused for the first refrigerant, and carbon dioxide is used for thesecond refrigerant, again as in the first embodiment.

The refrigerator according to the present embodiment includes controlmeans for closing the side of three-way valve 20 directed to coolingcompartment evaporator 12 when detecting that the temperature of coolingcompartment 21 has become a set value or lower. Further, it includescontrol means for closing the side of three-way valve 20 directed toheat radiation portion cooling evaporator 19 when detecting that thetemperature of freezing compartment 22 has become a set value or lower.It further includes control means for closing the side of three-wayvalve 20 directed to cooling compartment evaporator 12 and opening theside directed to heat radiation portion cooling evaporator 19 whendetecting that the temperature of freezing compartment 22 has become aset value or higher. It also includes control means for causing coolingcompartment cooling fan 23 to rotate by detecting the humidity ofcooling compartment 21 in the state where the side directed to coolingcompartment evaporator 12 is closed.

Otherwise, the configuration is identical to that of the firstembodiment, and thus, description thereof will not be repeated here.

The first refrigerant compressed by compressor 11 is passed through theheat radiators such as drain treatment refrigerant pipe 14, reduced inpressure and expanded in refrigerant expansion portion 13 a, anddelivered to cooling compartment evaporator 12, as shown by an arrow 35.After evaporated in cooling compartment evaporator 12, the firstrefrigerant is returned to compressor 11, as shown by an arrow 36, whereit is compressed again. Cooling takes place in cooling compartmentevaporator 12 by latent heat of the first refrigerant, as in the case ofthe first embodiment. The functions and effects of second circulationcircuit 6 are the same as those in the first embodiment.

A part of the first refrigerant is flown into auxiliary circuit 7 b viathree-way valve 20 formed between refrigerant condensation pipe 16 andrefrigerant expansion portion 13 a. The first refrigerant flowing intoauxiliary circuit 7 b is reduced in pressure and expanded in auxiliaryrefrigerant expansion portion 13 b, and delivered to heat radiationportion cooling evaporator 19, where it is evaporated. The firstrefrigerant coming out of heat radiation portion cooling evaporator 19merges with that in main circuit 7 a, and returns to compressor 11.

The first refrigerant reduced in pressure and expanded in auxiliaryrefrigerant expansion portion 13 b is in the two-phase state. When therelevant first refrigerant evaporates in heat radiation portion coolingevaporator 19; heat radiation portion cooling evaporator 19 attains alow temperature. High-temperature heat radiation portion 2 of Stirlingrefrigerating machine 1 is cooled, as heat radiation portion coolingevaporator 19 is in contact therewith. With this configuration, a partof the first refrigerant can be used to directly cool high-temperatureheat radiation portion 2 of Stirling refrigerating machine 1, so thatheat efficiency improves. This also improves the system COP. Further,high power output can be obtained even when low-temperature heatabsorption portion 3 of Stirling refrigerating machine 1 is in thecryogenic state, making it possible to maintain the cryogenic cooling offreezing compartment 22 for a long period of time.

The branch means can readily be formed by employing three-way valve 20.Further, when the one capable of opening/closing the side directed tocooling compartment evaporator 12 and the side directed to heatradiation portion cooling evaporator 19 is employed, the flow of thefirst refrigerant toward cooling compartment evaporator 12 or to heatradiation portion cooling evaporator 19 can be blocked as required,which contributes to saving of power consumption. Although three-wayvalve 20 of the present embodiment is arranged between refrigerantcondensation pipe 16 and refrigerant expansion portion 13 a, not limitedthereto, it may be arranged in any place of the piping betweenrefrigerant expansion portion 13 a and compressor 11. However, it ispreferable that the first refrigerant is sufficiently cooled in the heatradiators before it reaches auxiliary refrigerant expansion portion 13b, and thus, the valve is preferably arranged downstream of the heatradiators such as refrigerant condensation pipe 15.

By provision of the control means for closing the side of three-wayvalve 20 directed to cooling compartment evaporator 12 upon detection ofthe temperature of cooling compartment 21 being not higher than a setvalue, cooling of cooling compartment 21 can be interrupted when it isunnecessary. This can lower the load of compressor 11, and thus,contributes to saving of power consumption. Similarly, by provision ofthe control means for closing the side of three-way valve 20 directed toheat radiation portion cooling evaporator 19 upon detection of thetemperature of freezing compartment 22 being not higher than a setvalue, cooling of high-temperature heat radiation portion 2 of Stirlingrefrigerating machine 1 can be interrupted when it is unnecessary tocool freezing compartment 22. It can lower the load of compressor 11,again contributing to saving of power consumption.

Further, the refrigerator of the present embodiment includes the controlmeans for closing the side of three-way valve 20 directed to coolingcompartment evaporator 12 and opening the side directed to heatradiation portion cooling evaporator 19 when the temperature of freezingcompartment 22 has become a set value or higher in the case where thedoor of freezing compartment 22 is left open for a long period of timeor the like. Provision of this control means enables interruption of theflow of the first refrigerant toward cooling compartment evaporator 12,so that the cooling capacity of the first refrigerant is entirely usedfor cooling high-temperature heat radiation portion 2 of Stirlingrefrigerating machine 1. In this manner, high-temperature heat radiationportion 2 of Stirling refrigerating machine 1 can be cooled with a lowertemperature. This can increase the cooling capacity of low-temperatureheat absorption portion 3 of Stirling refrigerating machine 1, and as aresult, it is possible to quickly cool freezing compartment 22.

Further, the refrigerator of the present embodiment includes the controlmeans for causing cooling compartment cooling fan 23 to rotate bydetecting the humidity of cooling compartment 21 in the state where theside of three-way valve 20 directed to cooling compartment evaporator 12is closed. When cooling of cooling compartment 21 is unnecessary,cooling compartment cooling fan 23 is caused to rotate to increase thetemperature of cooling compartment evaporator 12. As such, the frostsettled over cooling compartment evaporator 12 is partially evaporated,to humidify cooling compartment 21.

Further, when the frost is settled around cooling compartment evaporator12 as its temperature becomes too low, the number of revolutions ofcompressor 11 is decreased and the output of Stirling refrigeratingmachine 1 is increased for defrosting, as in the case of the firstembodiment. Still further, the control means for detecting the outsideair temperature and the temperature of cooling compartment 21 and forcontrolling the number of revolutions of compressor 11 in response tothe outside air temperature and the temperature of the coolingcompartment is provided, again as in the case of the first embodiment.

The other functions and effects are identical to those of the firstembodiment, and thus, description thereof will not be repeated here.

It should be understood that the embodiments disclosed herein areillustrative and non-restrictive in every respect. The scope of thepresent invention is defined by the terms of the claims, rather than thedescription above, and is intended to include any modifications withinthe scope and meaning equivalent to the terms of the claims.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a refrigerator incorporating aStirling refrigerating machine and a compressor.

1. A refrigerator, comprising: a Stirling refrigerating machine having a high-temperature heat radiation portion and a low-temperature heat absorption portion and cooling a freezing compartment; and a compressor for circulating a first refrigerant through a first circulation circuit including a cooling compartment evaporator; wherein said high-temperature heat radiation portion is in physical contact with said first circulation circuit.
 2. The refrigerator according to claim 1, wherein said high-temperature heat radiation portion is in contact with piping of said first circulation circuit on its way from said cooling compartment evaporator back to said compressor.
 3. The refrigerator according to claim 1, wherein said high-temperature heat radiation portion is in contact with a heat radiation portion cooling evaporator that is formed in said first circulation circuit on its way from said cooling compartment evaporator back to said compressor.
 4. The refrigerator according to claim 1, comprising: a cooling compartment cooling fan for transferring cold heat of said cooling compartment evaporator to a cooling compartment; and control means for stopping said cooling compartment cooling fan when detecting that a temperature of said freezing compartment has become a set value or higher.
 5. The refrigerator according to claim 1, wherein said first circulation circuit includes a main circuit and an auxiliary circuit, said auxiliary circuit has an auxiliary refrigerant expansion portion and a heat radiation portion cooling evaporator formed downstream of said auxiliary refrigerant expansion portion, and has its inlet connected to branch means that is formed in piping of said main circuit on its way from said compressor to said cooling compartment evaporator, and said high-temperature heat radiation portion is in contact with said heat radiation portion cooling evaporator.
 6. The refrigerator according to claim 5, wherein a three-way valve capable of opening/closing its side directed to said cooling compartment evaporator and its side directed to said heat radiation portion cooling evaporator is arranged as said branch means.
 7. The refrigerator according to claim 6, comprising control means for closing the side of said three-way valve directed to said cooling compartment evaporator when detecting that a temperature of a cooling compartment has become a set value or lower.
 8. The refrigerator according to claim 6, comprising control means for closing the side of said three-way valve directed to said heat radiation portion cooling evaporator when detecting that a temperature of said freezing compartment has become a set value or lower.
 9. The refrigerator according to claim 6, comprising control means for closing the side of said three-way valve directed to said cooling compartment evaporator and opening the side of said three-way valve directed to said heat radiation portion cooling evaporator when detecting that a temperature of said freezing compartment has become a set value or higher.
 10. The refrigerator according to claim 6, comprising: a cooling compartment cooling fan for transferring cold heat of said cooling compartment evaporator to a cooling compartment; and control means for causing said cooling compartment cooling fan to rotate by detecting humidity of said cooling compartment in the state where the side of said three-way valve directed to said cooling compartment evaporator is closed.
 11. The refrigerator according to claim 1, comprising control means for decreasing the number of revolutions of said compressor and increasing output of said Stirling refrigerating machine when detecting that a temperature of said cooling compartment evaporator has become a set value or lower.
 12. The refrigerator according to claim 1, comprising control means for controlling the number of revolutions of said compressor in response to an outside air temperature and a temperature of a cooling compartment. 